This invention relates to reciprocating piston engines.
In one class of combustion engines, the engine includes reciprocating pistons which drive an eccentrically mounted cam shaft through piston and connecting rods. Such engines are subject to vibrations resulting from periodic unbalanced vertical inertia forces of pistons and connecting rods and lateral inertia forces created by crankshaft counterweights as they rotate. To reduce the effect of this vibration, multiple cylinders are frequently included.
In prior art types of this class of engine, vibrations are reduced by increasing the number of cylinders and the length of the connecting rods.
The prior art engines have several disadvantages such as: (1) a large number of cylinders increases costs and complexity, especially in diesel engines; (2) if long connecting rods are used, engine size is increased; (3) if the rod length to crank radius ratio is decreased, the ratio of inertia forces for the top of the stroke compared to the bottom of the stroke is increased, and the ratio of time that the piston spends in the upper half of the stroke as opposed to the lower half is decreased which respectively increases vibrational problems, decreases fuel burn time per revolution and limits maximum diesel RPM; and (4) the crankshaft deaccelerates the pistons as they approach the end of each stroke and then reaccelerates them, resulting in high stress on cranks, bearings and other components plus energy robbing friction.